The Z shelf by Miron Lior is, by all accounts, an awesome optical illusion.  Essentially, it presents five shelf surfaces in an undulating zigzag up and down the wall on which it’s mounted, with hidden bookends protruding from the edges and sitting flush with the books resting up against them, concealing their presence.  Hang one of these on your wall and your guests will stare in wonder at it from across the room, perplexed as to how your books are suspending themselves in mid-air.  It’s simple geometry, really, but they don’t need to know that.  The Z shelf was conceived in 2008 as a successor to the simpler (yet equally brilliant) Concept shelf from the same designer, which holds a stack of books at a perfect 90 degree angle, standing perpendicular against a wall and creating a similarly pause-worthy effect.  The wall-mounted brackets are also hidden by the books on each shelf; the only visible portion is the powder-coated steel shelf system itself, which spans 36 inches in height, 18 inches in width and 6 inches in depth.  It’s available directly from the designer for $250.